Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Patent
1996-11-07
1998-03-31
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
327108, 327111, 327157, H03K 300
Patent
active
057342792
ABSTRACT:
A charge pump circuit includes a current mirror circuit of current-sourcing and current-sinking FETs and a current steering circuit of cross coupled differential pairs of FETs. Nominal current flowing in the current-sourcing and current-sinking FETs is set. The current is for charging and discharging a capacitor of an external filter. During charging of the filter capacitor, the current through the current-sourcing FET is directed to the capacitor and the current through the current-sinking FET is directed from a low impedance voltage source. During discharging of the filter capacitor, the current through the current-sourcing FET is directed to the low impedance voltage source and the current through the current-sinking FET is directed from the capacitor. The current flowing in the current-sourcing and current-sinking FETs is nominally constant, regardless of the tri-state condition, charging or discharging, with the result that power supply noise is reduced. Current change in the power supply rails is reduced when switching from current-sourcing to current-sinking or vice versa. By using cascode FETs in both of the current-sourcing and current-sinking FET circuits, power supply noise rejection is improved.
REFERENCES:
patent: 5144156 (1992-09-01), Kawasaki
patent: 5334951 (1994-08-01), Hogeboom
patent: 5517142 (1996-05-01), Jang et al.
patent: 5592120 (1997-01-01), Palmer et al.
patent: 5656960 (1997-08-01), Holzer
Callahan Timothy P.
de Wilton Angela C.
Kim Jung Ho
Northern Telecom Limited
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